A color filter is a critical component for a liquid crystal display to achieve color display. The white light emitted from a backlight source irradiates onto the color filter, and passes through three (i.e. red, green, and blue) pigment color resists, which are set on the color filter to correspond to each pixel, so as to transmit red, green or blue light. Finally, a color image is formed by combining the pixels of different colors. The methods for producing pigment color resist on the color filter commonly used at present include a dyeing method, a printing method, an electrodeposition method, a pigment dispersing method, etc. The pigment dispersing method, due to its advantages in terms of the color properties, the image precision and the resistance to light and heat, becomes the mainstream method of production. The essential principle of the pigment dispersing method is to coat the pigment color resist agent on a transparent substrate, and then irradiate it with a light such as light from an ultraviolet lamp, so that the pigment color resist agent is solidified to form a color film layer. The pigment color resist agent comprises, among others, a pigment dispersion liquid, which essentially comprises a color pigment, a dispersion agent, a resin and a solvent.
In the pigment dispersion liquid, the pigment is generally dispersed in the solvent medium by means of mechanical ball milling or ultrasonic pulverization, and the pigment aggregates are broken into small particles under the effect of the external force. The dispersion agent is adsorbed on the surface of the pigment particle, which prevents the aggregation of the pigment particles and allows the pigment particles being dispersed stably and uniformly in the medium.
In order to improve the stability of the pigment dispersion liquid, most of the prior researches adopt a method of adding additives (such as dispersing resin, phase-supporting agent thereto. Although such method can improve the dispersivity of the pigment, it has a negative effect on the chromaticity of the pigment; and after the pigment forms the film, the purity and the saturation of the color of the pigment will be reduced. Additionally, due to the fixity of the color of the pigment, it is difficult to adjust the pigment dispersion liquid to a desired chromaticity.